Fix dtype type hints

Author: aaronchucarroll

pandas/core/arrays/arrow/array.py

@@ -2534,7 +2534,7 @@ def _str_findall(self, pat: str, flags: int = 0) -> Self:
         return type(self)(pa.chunked_array(result))
 
     def _str_get_dummies(
-        self, sep: str = "|", dummy_na: bool = False, dtype: NpDtype = None
+        self, sep: str = "|", dummy_na: bool = False, dtype: NpDtype | None = None
     ):
         if dtype is None:
             dtype = np.bool_

pandas/core/arrays/categorical.py

@@ -2745,7 +2745,7 @@ def _str_map(
         return take_nd(result, codes, fill_value=na_value)
 
     def _str_get_dummies(
-        self, sep: str = "|", dummy_na: bool = False, dtype: NpDtype = None
+        self, sep: str = "|", dummy_na: bool = False, dtype: NpDtype | None = None
     ):
         # sep may not be in categories. Just bail on this.
         from pandas.core.arrays import NumpyExtensionArray

pandas/core/arrays/string_arrow.py

@@ -552,7 +552,7 @@ def _str_find(self, sub: str, start: int = 0, end: int | None = None):
         return self._convert_int_dtype(result)
 
     def _str_get_dummies(
-        self, sep: str = "|", dummy_na: bool = False, dtype: NpDtype = None
+        self, sep: str = "|", dummy_na: bool = False, dtype: NpDtype | None = None
     ):
         if dtype is None:
             dtype = np.int64